The present invention relates to a miniature contactless switching unit, and more particularly, to a switching unit in which a magneto-electro converter is assembled. For years, limit switches or reed switches have been employed in order to detect the position of moving members. However, some applications require performance beyond that obtainable with mechanical-to-electronic interface devices. In their search for performance, attention to non-contacting switch assembly, such as photoelectric switches or `HALL EFFECT` switches has been drawn.
Regarding photoelectric switches, an improvement in switch life, speed and reliability has been made in comparison with conventional contacting switches. However, the photoelectric switches are complicated in construction and their cost are considerably high.
Reference is made to conventional magnetic non-contacting switches employing magneto-electro converter, such as molded Hall integrated circuit (Hall IC). The Hall IC includes a silicon Hall cell, amplifier, trigger and output stage integrated with its own voltage regulator onto a monolithic silicon chip. The switch assembly comprises the Hall IC chip, and a magnet oppositely disposed to the Hall IC chip. Switching action is dependent on the proximity of an external magnet whose magnetic flux passes perpendicularly through the Hall cell on the chip face. As the external magnet is moved towards the Hall cell, the cell produces an analogue voltage proportional to the magnetic field intensity.
Although the application of the `HALL EFFECT` switches stated above to various kinds of devices results in favorable high performance switching characteristics, some drawbacks mainly caused by moving the magnet with respect to the Hall IC chip are pointed out as follows:
First is that, with the moving magnet, it is difficult to form an uniform magnetic field because of the fact that magnetic flux density depends on a distance between the external magnet and the Hall IC. For this reason, high reliability in switching action cannot be obtained. Moreover, strict conditions on performance of the magnet is required since undesirable influences in forming the magnetic field are apt to occur, provided the magnet lacks in homogeneousness with respect to quality.
Second is that it is difficult to determined positioning or matching of the magnet and the Hall IC because of the fact that it is necessary to take into account the time during which the magnet passes over the Hall IC, the traveling speed of the moving magnet, and other parameters.
Third is that it is difficult to reduce the size of the magnet because of the fact that it is necessary to make an allowance for a displacement from the predetermined position due to the inertia force of the moving member. Fourth is that it is difficult to fabricate the magnet which is satisfactory to the above requirements.